Bundling strap



Nov. 5, 1968 Filed Aug. 7, 1967 F'IG.3

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m E R m M F E u as m P a m 0 1 1 D F I G a N m m I D D ll 3533 meme United States Patent 3,408,699 BUNDLING STRAP Frank J. Reynolds, North Brunswick, N.J., assignor to The Thomas & Betts C0., Elizabeth, N.J., a corporation of New Jersey Filed Aug. 7, 1967, Ser. No. 658,944 Claims. (Cl. 2416) ABSTRACT OF THE DISCLOSURE The disclosure is directed to an improved bundling strap of the type which consists of an elongated relatively flat strap having at one end a tapered tail section and at the other end a head portion. The head portion includes an aperture for the passage of the tail-end tapered portion therethrough after it has been passed about a bundle of wires. The head portion includes in its aperture a flexure restraining means such that the tapered-tail portion of the strap may be inserted through the aperture of the head portion to form said cable bundle, but that when attempts are made to withdraw the strap from the head portion, the flexure restraining means prevents such removal, thus assuring that the strap remains locked in its cable bundling position. The improvement consists of modifications to the flexure restraining member found in the aperture of the head portion. These modifications reduce the resistance of said flexure restraining member to the insertion of the strap into the aperture of the head portion, while increasing the resistance of said flexure restraining member to the withdrawal of the strap from the head-end portion. The decrease in insertion resistance is accomplished by weakening the flexure restraining member at its flexure region. The increased Withdrawal resistance is accomplished by strengthening the flexure restraining member. This weakening is achieved in any of a number of way-s. Firstly, material may be removed from the flexure restraining member at its flexure region, that is the region of flexure during insertion. Additionally, the dimensions of the flexure restraining member may be changed so that the portion at/ or adjacent the flexure region is thinner than the remainder of the flexure restraining member. Such weakening can also be produced by chemical treatment or processing such as by annealing the two sections of the flexure restraining member differently or in the alternative the upper portion of the flexure restraining member, that is above the flexure region may be strengthened by adding tabs or by other stilfening means or by forming.

BACKGROUND OF THE INVENTION Field of the invention The invention is directed to the field of bundling of electrical wire or the like, into uniform cables which may be treated more easily than would be possible with a plurality of discreet unbundled wires. The invention replaces prior techniques, where it was necessary to tie, by means of waxed cords the various wires which made up a cable or which were to be routed along a given path. The problems with such prior art devices are obvious. If it was desired to shorten the wires which made up the cable, the bundling cord would also be cut causing it to unravel, thus destroying the bundling and requiring a relacing of the cable.

Description 0 f the prior art In prior art cable bundling strap devices, the problems generally described above were overcome but introduced certain other problems related to their use. These devices, make use of a solid flexure restraining member. The flexure restraining member had to be chosen in such a manner as to have a reasonably high pull-out force, that is the force resisting the removal of the bundling strap from the head-end portion, but at the same time could not have such a high pull-out force that it would make the insertion force, required to insert the tapered-tail portion of the strap into the head-end portion excessive. Further, variations in the clearance between the strap engaging edge of the flexure restraining member and the opposite surface of the aperture of the head portion, greatly alter the insertion and pull-out forces. For example, if the clearance was too great the insertion force would be decreased while the pull-out force would remain approximately the same. If the clearance was too small the insertion force would be increased as would the pull-out force.

SUMMARY OF THE INVENTION The present invention makes possible a cable bundling strap which both minimizes the insertion force required to place the tapered tail-end portion of the strap into the head end portion while at the same time provides maximum pull-out force against the attempted withdrawal of the strap from the aperture in the head portion. This is achieved by the use of a flexure restraining member which has varying stiffness characteristics along its length. A first area, of its overall dimension, will be the area from the flexure region to the strap engaging end. The second area will be from the flexure region to the opposite end. By controlling the transition or flexure region between these areas, or by altering one of the areas, minimum insertion force and maximum pull-out force will be achieved. This desired result is achieved in a plurality of ways. Firstly, material may be removed at the transition or flexure region or the transition or flexure region and/ or the second area may be made narrower, thinner or may be scored. In addition the transition or flexure region and/or the second area may be treated in a manner different than that of the remaining portion of the flexure restraining member so as to have less stiffness than that of the remaining portion. Alternatively, rather than weaken in some manner the second area, the first area, that is the area extending from the transition or flexure region to the strap engaging edge may be strengthened by deforming it (e.g., a rib or shovel like form), or by the addition of a rib or other supporting structure to make this portion stiffer than the remainder. Thus, by weakening the flexure restraining member at its flexure region, as described above, minimum insertion forces can be achieved whereas by making the flexure restraining member stiffer within the first area (between the insertion flexure point and the strap engaging end) maximum pull-out force can be achieved. It is therefore an object of this invention to provide an improved form of bundling strap.

It is yet another object of this invention to provide an improved form of bundling strap which minimizes insertion force requirements while maximizing the withdrawal force requirements.

It is still another object of this invention to provide an improved form of bundling strap employing a unique stiffened flexure restraining member so arranged as to be weakened at its flexure region whereby minimum insertion force is required while maximum pull-out force is required.

Other objects and features of this invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle invention, and the best modes which have been contemplated for carrying it out.

Brief description of the drawings FIG. 1 is a front elevation of a flexure restraining member as found in the prior art.

FIG. 2 is a side elevational view of the prior art flexure restraining member as shown in FIG. 1.

FIG. 3 is a graph ilustrating the force-distance relationship exhibited by the flexure restraining member shown in FIGS. 1 and 2.

FIG. 4 is a front elevational view of the bundling strap constructed in accordance with the concepts of this invention.

FIG. 5 is a sectional side elevation of the device of FIG. 4 taken in along the line 5-5.

FIG. 6 is a front elevational view of the flexure restraining member employed with the bundling strap of FIG. 4 and constructed in accordance with the concepts of the invention.

FIG. 7 is a further embodiment of the novel flexure restraining member of the invention.

FIG. 8 is a further embodiment of the novel flexure restraining member shown in FIG. 6.

FIG. 9 is yet another embodiment of the novel flexure restraining member as shown in FIG. 6.

FIG. 10 is a further embodiment of the novel flexure restraining member as shown in FIG. 6.

FIG. 11 represents a sectional side elevation of the device of FIG. 10 taken along the line 11-11.

FIG. 12 is a force-distance graph illustrating the rela tionship between the insertional and pull-out forces and the displacement of the flexure restraining member constructed in accordance with concepts of this invention.

FIG. 13 is a side elevation of a further embodiment of the novel flexure restraining member of the invention.

Similar elements are given similar reference characters in each of the respective figures.

Description of the preferred embodiment Referring now to FIGS. 1 and. 2 there is shown a prior art form of a flexure restraining member having a generally rectangular body portion 22 and having a knife edge 24 at one end thereof. As can be seen from the figures, the width, length and thickness of the flexure restraining member 20 are generally uniform throughout the body except for the knife edge 24. The flexure restraining member 20 is inserted into an aperture as is shown in the sectional view of FIG. 5, such that a portion thereof is within an aperture in the head-end portion of the strap while the remaining portion extends into an aperture 46 within the head-end portion.

Turning now to FIGS. 4 and 5, the cooperations between the flexure restraining member and the remaining portion of the bundling strap may be understood. 'The bundling strap 40 has a tapered tail-end portion 42 and a head-end portion 44, having an aperture 46 therethrough. The head-end portion 44 has a leading edge 48 and a trailing edge 50. Further, the aperture 46 is bounded by a top surface 62 and two bottom surfaces 58 and 64 separated from surface 62 by different distances. The surface 58 in FIG. 5 is a greater distance away from the surface 62 of the aperture 46 than the surface 64. A flexure restraining member 52 is placed in an aperture within the head-end portion 44 to permit the strap engaging edge of the member 52 to extend into and partialy block aperture 46. The portion of member 52 shown in dotted line in FIG. 4 is referred to as the second portion or second area and is designated 54. The portion remaining and extending into the aperture 46 is referred to as the first portion or first area and is designated 56. The flexure region occurs at the contact between surface 58 of aperture 46 and the member 52 and is identified as 66. A pull-out failure region 68 occurs at the contact between surface 64 and the member 52.

In the event that a flexure restraining member such as that shown by 20 in FIGS. 1 and 2 were inserted in the aperture 46, the same' general stiffness would be exhibited in all areas of the flexure restraining member 20 and there would be no difference in the ability of the flexure restraining member to respond to insertion or pull-out forces. The forces required to insert the straps would then be dependent on the stiffness of the flexure restraining member 20 and of the distance between the knife edge 24 of the flexure restraining member 20 and the surface 62 of the transverse aperture 46 of the head-end portion 44. The relationship between these forces and the distance being described is illustrate-d in FIG. 3 wherein there is shown a graph of force against the distance D, which as shown in FIG. 5, is the distance between the knife edge of member 52 and surface 62. The first distance D1 shows the initial spacing of the knife edge 24 with respect to a surface such as surface 62. The graph generally follows the form of a plot of the modulus of elasticity having at its lower end a generally linear portion and finally shows a knee which indicates exceeding the yield point :of the material causing it to go into a deformed condition which will not allow it to return to its original state when the forces are relaxed. As a result of the insertion of the tail-end portion 42 of the strap 40 into the transverse aperture 46 within the head portion 44 of the strap 40, the flexure restraining member 20 will be deflected to a position shown as A in FIG. 3. As soon as the insertion is completed the flexure restraining member 20 will be allowed to return to some new position B which is dependent upon the thickness of the body portion of the strap 40, the strap 40 material, the member material, etc. The position A represents the force required to deflect the flexure restraining member 20 which is proportional to the insertion force whereas the position B represents the force of the flexure restraining member 20 on the strap 40 after the flexure restraining member 20 engages and digs into the strap. Variations in the positioning of the flexure restraining member 20 within an aperture such as aperture 46 of FIG. 5 will change the initial position D1. Changes in the material of which the flexure restraining member 20 is constructed, will further change the position but not the general form of the curve shown.

Referring now to FIG. 6 there is shown a flexure restraining member 70 constructed in accordance with the concepts of the invention. As is shown in the figure, the flexure restraining member 70 has a body portion 72 intersected near its lower end by line EE. The portion of the body 72 between the line E-E and the knife edge 74 is the first body area 76. A second portion 78 between the bottom edge and the line EE is the second body area 78. In the approximate center of the width of the body 72 and centered about the line EE is an aperture 80 which causes a weakening or a decrease of stiffness of the flexure restraining member 72 along the line EE. Flexure restraining member 70 will be inserted into an aperture in the headend portion 44 of the bundling strap 40 as shown on FIGURE 4. The insertion of the flexure restraining member 70 in this manner provides at the flexure region 66 an area of reduced stiffness of the flexure member 70 thus decreasing the amount of insertion force required to place the tapered tail-end portion 42 of the strap 40 within the transverse aperture 46.

When withdrawal of the strap 40 is attempted the flexure restraining member 70 flexes about the flexure region EE and is restricted in its movement toward the leading edge 48 of the head-end portion 44 by the surface between surfaces 58 and 64. Should the flexure restraining member 70 be forced too far towards leading edge 48, failure may occur at point 68. To prevent such failure it is desirable to increase the stiffness of first body area 76 particularly in the region indicated as R.

In summary, flexure occurs about the region 66 shown in FIG. 5 which portion of the flexure restraining member 70 is weakened by the aperture 80 whereas the withdrawal is dependent upon the stiffness characteristic of the first body area 76. The relative forces upon this flexure restraining member 70 during the insertion and attempted withdrawal of the strap 40 are illustrated in the graph of FIG. 12, which shows the forces present when the flexure restraining member 70 is deformed beyond its yield point. Again the point D1 describes the initial location of the knife edge 74 with respect to the surface 62 of the transverse aperture 46 shown in FIG. 5. The curve of FIG. 12 shows that the deformation occurs at a lower force level than that shown in FIG. 3. As a result of the insertion of the tapered tail-end section 42 of the strap 40 into the aperture 46, the modulus of the flexure restraining member 70 will be exceeded and some permanent deformation will occur as a result, as shown at points F, F' and F". Where the points F, F, and F" represent the insertion forces of flexure restraining members 70 having different distances between the knife edge 74 and the surface 62. This plot illustrates that a lower insertion force is required to insert the tapered tail-end portion 42 of the strap 40 into the transverse aperture 46 and that variation in positioning of the flexure restraining member 70 will give the same forces. After the strap insertion has been completed the force levels will drop from the points F, F or F" showing the total insertion force, to the points G, G or G" respectively. Similarly, the distance of separation between the knife edge 74 and the surface 62 will decrease. Variations in the positioning of the knife edge 74 of the flexure restraining member 70 within the aperture 46 will mainly result in different distances being achieved with different force levels. However, these force levels will not vary greatly.

Turning now to FIG. 7 a further embodiment of the flexure restraining member of FIG. 6 is shown. The flexure restraining member has a knife edge 88 and has a large opening 90 extending about the line EE. Positioning of the flexure restraining member 86 will be similar to that of flexure restraining member 70 in the aperture 46 of FIG. 5. It is also possible to form the same weakened area by removal of material by tapering the sides of the portion of the flexure restraining member 86 below the line EE. In addition two holes may be placed at the edge or anywhere along the line EE in order to achieve the desired weakening effect.

Referring to FIG. 8, a further embodiment of the device of FIG. 6 is shown. The flexure restraining member 92 as shown in FIG. 8 may be suitably weakened to decrease the insertion forces by means of scoring along the line EE or by making the portion below the line EE thinner than that above the line EE as shown in FIG. 13, wherein the second body area 122 of flexure restraining member 120 is thinner than the first body area 124. Further it is possible to specially treat or anneal the area about the line EE to provide the weakening effect or to process in a different fashion the portion above the line E-E and the portion below the line EE. Additionally, by etching or other chemical or mechanical processing the stiffness of the area above the line EE and not below the line EE, may be made dissimilar, the weaker section being below the line EE.

Now, referring to FIG. 9, another method of achieving the differences in stiffness between the two areas of the flexure restraining member 100 may be achieved. In

FIG. 9 the stiffness of the first body area is increased by the addition of a rib 102 in that area of the flexure restraining member 100. Although a single rib 102 is shown, any arrangement of ribs or a honeycomb or any other similar effect may be employed to provide addition-a1 stiffness to the upper portion of the flexure restraining means above the line EE. In FIGS. 10 and 11, there are shown another alternative arrangement providing increased stiffness of the first body portion of the flexure restraining member 106. This is achieved by the punching of a rib 108 into the first body portion of the flexure restraining member 106 above the line EE. Again, although a single rib 108 has been shown to be formed into the first body portion of the flexure restraining member 106, a plurality of ribs may be so punched or a general shovel like effect may be achieved to increase the stiffness of the area above the line EE of the flexure restraining member 106.

While there has been shown and described and pointed out the fundamental novel features of the invention, as applied to the preferred embodiments, it should be understood that various omissions and substitutions and changes of the form and details of the devices illustrated, and in their operation may be made by those skilled inthe art, without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A self-clinching bundling strap comprising: a headend portion, a tail-end portion and a body portion therebetween; said head-end portion having a transverse aperture therethrough and including an eyelet portion projecting from one side of said head-end portion; said head-end portion having a further aperture therein communicating with said transverse aperture; and a flexure member, having two distinct areas along its length, a first area having a first predetermined stiffness characteristic inserted into said further aperture, while the second area, having a second predetermined stiffness characteristic, extends into said transverse aperture partially blocking same, and presenting an end generally transverse to said transverse aperture, said flexure member position providing a stilfness transition region adjacent the jointure of said transverse aperture and said further aperture; said flexure member transverse end being formed to engage in a locking manner the body portion of said strap in minute move ments of adjustment against relative reverse movement when looped upon itself through said aperture.

2. A self-clinching bundling strap as defined in claim 1, wherein said first area of said flexure member is weakened by the removal of a portion thereof.

3. A self-clinching bundling strap as defined in claim 1, wherein said first area of said flexure member is of different dimensions than said second area of said flexure member.

4. A self'clinching bundling strap as defined in claim 1, wherein said first area of said flexure member is thinner than said second area of said flexure member.

5. A self-clinching bundling strap as defined in claim 1, wherein the transition region between said first and second areas of said flexure member is scored to weaken said flexure member thereat.

6. A self-clinching bundling strap as defined in claim 1, wherein said first and second areas of said flexure member have predetermined stiffness characteristics caused by differences in the processing of each distinct area.

7. A self-clinching bundling strap as defined in claim 1, wherein said transition region is weakened.

8. A self-clinching bundling strap as defined in claim 1, wherein the stiffness of said second area of said flexure member in increased by deformation.

9. A self-clinching bundling strap as defined in claim 1, wherein the stiffness of said second area of said flexure member is increased by adding support means thereto.

10. A self-clinching bundling strap as defined in claim 1, wherein said flexure member is composed of two areas ofdiiferent materials having diiferent stiffness character- 3,157,421

istics joined at said transition region. 3 13 047 References Cited 23 331 UNITED STATES PATENTS 5 3 7 1 6,696,570 4/1902 Kimball 2415O 2,626,825 1/1953 Stofi'el 292-322 XR Nierhaus 292-322 Schwester et a1. 2416 Geisinger 24-16 Geisinger 1- 24-16 DONALD A. GRIFFIN, Primary Examiner. 

